An increasing number of users of stored information are facing requirements of expanded storage capacity, faster retrieval, and lower cost than found in prior art data storage systems. Therefore, there has been a move to denser and denser magnetic disks and tapes, and, more recently, to optical disks and optical tapes.
The article entitled "Terabyte Optical Tape Recorder" by K. Spencer, in Ninth IEEE Symposium On Mass Storage Systems, Oct. 31-Nov. 3, 1988, Monterey, Calif., at pages 144-146, discloses a CREO Products, Inc. optical tape recorder. The CREO recorder uses a tape transport comprising three direct drive motors, and a linear scanner including laser diodes with associated optics, a slide with a mirror mounted thereon, an air bearing wherein the slide moves longitudinally, and an optical encoder. To write bits across the optical tape, the slide moves longitudinally within the air bearing to move the mirror transversely to the width of the optical tape while the light encoded data is reflected from the mirror and onto the optical tape. In operation, the recorder scans across the optical tape in a first direction to record bits of information across the tape. The tape then steps in a predetermined direction, and the linear scanner crosses the optical tape in a second opposite direction to write a next record. The CREO recorder writes 32 data bits at a time, and as the linear scanner goes across the tape it writes four bytes of information by 20,000 bytes thus giving an 80 kilobyte physical record. The CREO optical tape recorder has a sustained data rate of three megabytes per second using a 1.5 micron spot spacing on the optical tape, and a head-to-tape speed of 36 meters per second.
U.S. Pat. No. 4,815,067 (E. Webster et al.), issued on Mar. 21, 1989, discloses a helically scanned optical rotary headwheel tape and replay system. The system comprises a rotating drum with a galvanometer mirror for controlling the tracking of a number of write and read light beams during recording and replay. Dynamic focussing of the light beams on the recording medium is controlled by means of a voice-coil actuator operating on a lens situated outside the drum. An optical rotator is provided through which combined write and read light beams pass. The optical rotator is driven by a motor to rotate at half the rotational velocity of the drum. This presents an image to the optical tape which rotates synchronously with the drum.
It is desirable to provide an optical tape data storage system which performs at high data rates (e.g., at least 100 megabytes per second) and is adaptable to different tape widths and extended data rates.